PROJECT SUMMARY Wound care is a major challenge to the public health, and the burden is rapidly growing due to increasing health care costs, an aging population and a sharp rise in the incidence of disease such as diabetes and obesity that contribute to poor wound healing. While multiple factors may contribute to complications associated with wound healing, compromised tissue repair represents an underlying cause for non-healing wounds. A recent series of studies by the investigator?s team identified a novel TRIM family protein named MG53 as an essential component of the cell membrane repair machinery. Here we provide evidence that MG53 is a vital component of wound healing and that topical application of recombinant human (rh)MG53 protein has potential to promote healing of chronic wounds. MG53 is capable of nucleating the membrane repair machinery in keratinocytes, therefore protecting injuries to the epidermis. MG53 present in the extracellular solution can facilitate migration of fibroblasts in response to scratch wounding, thus contributing to efficient reepithelization of wound closure. Moreover, we made a novel finding that links circulating MG53 to the engagement of epithelial stem cells during the chronic and remodeling phase of wound closure. While epithelial stem cells do not express endogenous MG53 protein, they can take up MG53 from circulation in response to dermal injury. Therapeutic efficacy of rhMG53 will depend on the formulation as well as the approaches of delivering MG53. Direct administration of MG53 to the wound site and indirect delivery by intravascular injection are possible approaches, but will have low efficacy due to the short half-life of MG53 in blood circulation. It is important that we develop a proper formulation for sustained delivery of rhMG53 to the wound site in order to enhance therapeutic efficacy. The goal of this project is to test the hypothesis that MG53 facilitates healing of chronic wounds by enhancing cell membrane repair and epithelial stem cell function, and hydrogel formulation of rhMG53 represents an effective means for dermal wound healing. Three specific aims are proposed: a) elucidate the mechanisms that underlie MG53?s function in wound healing (Aim 1); b) develop hydrogel-based delivery of rhMG53 to treat dermal wound (Aim 2); and c) conduct proof-of-concept study on rhMG53/hydrogel for chronic wound healing application (Aim 3). Fulfillment of these studies should advance our knowledge on the biology of MG53 in wound healing and lay the foundation for translational application of rhMG53 in treating chronic wounds in the elderly population.